Recently, as wireless communication technology that can be applied to an electronic device or the like, for example, Bluetooth is known. By using the wireless communication technology of Bluetooth, audio data can be transmitted from a mobile information terminal such as a cellular phone or a portable music player to an external device such as a headset without using an audio cable.
As a profile for audio data transmission, for example, “Advanced Audio Distribution Profile (A2DP)” (Advanced Audio/Video Distribution Profile (Bluetooth SIG)), “Generic Audio/Video Distribution Profile” (Generic Audio/Video Distribution Profile (Bluetooth SIG)), or the like are known. These are specifications for transmitting real-time audio data in a streaming manner between devices having a Bluetooth connection.
For example, in a mobile information terminal such as a cellular phone or a portable music player, audio data is coded by using a format such as SBC (Sub Band Coding), MP3 (MPEG1 Audio Layer-3), ATRAC (Advanced Transform Acoustic Coding) 3, or the like and the coded data is transmitted in units of packets. An external device such as a speaker or a headset reproduces data right after reception of the data without waiting for reception of all the packets. Accordingly, a user can listen to the sound from the mobile information terminal, the portable music player, or the like in almost real-time by using the external device such as a speaker or a headset.
In addition, as technology for preventing the replication (copy) of digital contents such as audio data, SCMS-T (Serial Copy Management System-T) has been proposed. This SCMS-T is one of methods of protecting digital contents defined in “A2DP Spec V 1.0 Sec. 11 Appendix A: Audio Streaming with Content Protection”. According to the SCMS-T, in order to prevent audio data transmitted in accordance with A2DP from being directly recorded in a device or output to any other device in view of copyright protection, indication of prevention of recording or outputting the audio data is sent to a device such as a headset. For this indication, 2 bits (CP-bit and L-bit) used for a copy control process in SCMS-T are inserted into a packet format as a CP (Content Protection) header, and the 2 bits (CP-bit and L-bit) are transmitted to an external device such as a headset.
Accordingly, for an external device such as a headset that does not support SCMS-T, reproduction of transmitted audio data is not allowed, and thus the transmitted audio data is not reproduced by the external device. In other words, reproduction of the transmitted audio data is allowed only for an external device such as a headset that supports SCMS-T, and thus the transmitted audio is reproduced by the external device.
In specifications defined by “Advanced Audio Distribution Profile (A2DP)” or “Generic Audio/Video Distribution Profile”, a sequence of a negotiation process for various parameters such as the type of a codec, a sampling rate, and a bit rate of audio data to be transmitted or received which is performed in advance between a device having audio data (audio source) and a device receiving the audio data and a process of starting streaming transmission is defined. In addition, according to the specifications, a streaming transmission process is allowed to be started from any side between the device (SRC) having the audio data and the device (SNK) receiving the audio data.
However, when a negotiation process is performed by the lead of the device (SNK) receiving the audio data so as to start the streaming transmission process, the device (SNK) receiving the audio data cannot know various parameters such as the type of codec, a sampling rate, a bit rate, attribute information indicating whether a content requires copyright protection, and the like of the audio data transmitted from the device (SRC) having the audio data at a time when the negotiation process is started, and generally, standard parameters are designated as various parameters for starting the streaming transmission process assuredly. In other words, a standard SBC is designated as the type of the codec for the audio data, and standard values should be designated for the bit rate and the sampling rate. Even it is designated whether a CP header for adding copy control information of audio data is included, it cannot be determined that designation of inclusion of the CP header appropriate for the content can always be made. Accordingly, there is a problem that parameters optimal to the device (SNK) receiving the audio data or the like cannot be selected and set.